The present invention relates to an ozone producing apparatus. More particularly, it relates to an ozone producing apparatus for continuously producing ozone and storing the same in an adsorbed state and supplying the ozone when required by desorbing (separating) the same.
While a large quantity of cooling water is used at power stations and in chemical industries, microorganisms or seaweed in the water cause slime hazards and thereby resulting in blockage of canals or deterioration of heat exchange efficiency. One method which might be taken as a countermeasure to prevent such troubles is to employ ozone water of high density. In order to produce high density ozone water, it is more advantageous to employ a so-called intermittent ozone producing method, wherein a small sized ozone generator of small capacity is used to store the produced ozone by using an adsorbent over a long period and to take this stored ozone out from the adsorbent when required for producing high density ozone water, than producing ozone with an ozone generator of large capacity, in view of initial and running costs.
An ozone producing apparatus employing such an ozone producing method is known to comprise the following components as shown in FIG. 13: an ozone generator 50, an oxygen supply source 51, a circulating blower 52, an adsorption/desorption tower 53, a cooling source 54, a heating source 55, a water flow ejector 56 and switch valves 57a to 57g. The adsorption/desorption tower 53 is of double cylinder type of which inner cylinder is filled with an ozone adsorbent and an outer cylinder with heating medium. Silica gel might be employed as the ozone adsorbent, and ethylene glycol or alcohol group as the heating medium. It should be noted that the circulating blower 52, ozone generator 50 and adsorption/desorption tower 53 constitute, in this order, a circulating system.
Operations of the apparatus will now be explained. There are two operations in total, namely ozone adsorbing operation, and ozone desorbing operation.
The adsorbing operation will first be explained. Oxygen is supplied by the oxygen supply source 51 so that the pressure in the circulating system OL is always constant. In this case, the pressure is normally maintained at 1.5 kg/cm.sup.2. When oxygen is made to flow in the circulating system by the circulating blower 52 while the switch valves 57c and 57d are in an opened condition, a part of the oxygen is converted into ozone to generate an ozonized oxygen while passing through the discharge space of the ozone generator 50, and the ozonized oxygen is then transferred to the adsorption/desorption tower 53. The adsorbent in the adsorption/desorption tower 53 selectively adsorbs ozone, and the remaining oxygen is returned to the circulating blower 52 through the switch valve 57c. Oxygen which has been consumed as ozone to be adsorbed is supplemented through the oxygen supply source 51. Since the adsorbent assumes a property that adsorption capacity of ozone varies depending on temperature, the adsorbent is cooled by the cooling source 54 to not more than -30.degree. C. That is, the lower the temperature becomes, an amount of ozone adsorption increases, while the higher the temperature becomes, it decreases. Accordingly, the temperature of adsorbent is raised by the heating source 55 when desorbing ozone.
When the adsorbent in the adsorption/desorption tower 53 has adsorbed ozone to approach the ozone saturation adsorption amount, the desorbing operation of ozone is performed. In the desorbing operation, operations of the ozone generator 50, circulating blower 52 and cooling source 54 are terminated and the switch valves 57a to 57d are closed. Thereafter, the heating source 55 and water flow ejector 56 start their operation and switch valves 57e to 57g are opened. At this time, temperature of the adsorbent is raised by applying heat through the heating source 55 so that ozone which has been adsorbed by the adsorbent can be easily desorbed therefrom. By depressing to suck ozone in the adsorption/desorption tower 53 by means of the water flow ejector 56, ozone is dispersed into water in the water flow ejector 56 to be dissolved and sent to, as ozone water, places where it is used. When the desorbing period is completed in this way, the process returns to the initial adsorbing operation and is continuously repeated.
Depending on the temperature of the water or on the degree of pollution of the water, the speed of multiplication of microorganisms and seaweed in water which cause slime hazards varies as well as the reactive speed of ozone. Therefore, the amount of required ozone also varies depending on seasonal fluctuations of water temperature or fluctuations in the degree of pollution of the water. However, the amount of stored ozone can not be adjusted in a conventional apparatus, so that it might often happen that ozone can not be provided to be just sufficiently enough for removing slime. That is, when the amount of ozone is small, there can not be achieved normal slime adhesion preventing effects, and when the amount of ozone is large, it is not only uneconomical but might also cause generation of oxidants when applied to sea water wherein ozone reacts with brominated ion in the sea water to generate oxidants so that a decomposing device for such oxidants will be required, resulting in a large sized apparatus.
Further, when a conventional apparatus is continuously used over a long term, the amount of stored ozone might also be varied due to changes in ozone adsorbing performance of silica gel or changes in the performance of the ozone generator and might cause abundance/shortage of ozone.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an ozone producing apparatus which is economical and with which hardly no byproducts such as oxidants are generated by continuously storing an amount of ozone required for obtaining suitable slime removing effects in accordance with fluctuations of qualities or temperature of water.